In the posterior treatment of spinal deformities, pedicle screws or hooks are used to connect vertebral bodies to a longitudinal rod. Prior to implantation, the longitudinal rod is shaped in a particular form so as to correct the deformity of the vertebral column. This technique has proved successful and meanwhile has come to be considered as state of the art.
Despite the development of new connecting techniques, such as the use of jaws with polyaxial bearings to connect the screws and the longitudinal rod, the intra-operative connection of the two elements remains problematic, particularly in cases of heavy spinal deformities. The problem lies in the fixed distance between the head of the pedicle screw and the longitudinal carrier. In other words, the polyaxial bearing of the screw head within the connecting jaw allows for variable screw angles but not for variable distances between the screw head and longitudinal rod carrier. A variable distance between the screw head or the end portion of the hook and the longitudinal rod carrier is desirable as it is not always possible to achieve 100 percent alignment of the vertebral column relative to the longitudinal rod.
It is accordingly an object of the invention to create an apparatus for connecting a pedicle screw or a pedicle hook to a longitudinal rod which provides a polyaxial bearing for the pedicle screw or pedicle hook and also provides a pivotable connection between the connector and the longitudinal rod, pivotable connection being lockable in any desired position.